Baba - I agree with MrsK that the range of days they gave you seems way too close to AF. An OPK is kinda like a pregnancy test, except it's testing for different hormones. It tests for the lutenizing hormone (LH) which is what triggers ovulation. Once you get a positive on an OPK, you will typically ovulate within 12-36 hours. Another thing you can look for and chart is your CM (cervical mucas). Once you get fertile CM, which is either egg white (the clear stretchy kind) or watery, that means in most women that you're entering your fertile window. Those are the best ways to predict when you're most fertile. Don't worry...you'll learn all of this stuff with time.
lsd - don't worry - I'm doing the same thing! I cant help it. You don't even want to know how many times in the last 2 days I've stood in the mirror analyzing and staring at my tatas! I'm convinced they look different...little purple veins everywhere that aren't normally there...which (in combination with other symptoms) then brings on the "omg, could I be pregnant? No. Wait. Maybe!" Every time I walk by a mirror, up goes my shirt. I've lost my mind. And I'm setting myself up for disappointment again.
Reggie - I'd discard it. It's so different than the rest of your temps that it almost has to be inaccurate. I think you made the right call.